Spoiler alert - don't watch the end of the video if you don't want to see the end of the game.
This elevator bit is pretty tough, and really took a lot of practice to get by without dying. Anticipate where the enemies will be and try to kill them before they can shoot or overwhelm you.
The last boss is harder than it looks. The first two phases are easy to learn, but take a long time. Once the eyeballs come out, the attacks get really low tolerance and unforgiving. I died a LOT figuring it out. The final form isn't hard, but be careful when you jump cause it moves the platform out from under you.
Sorry for the poor quality, I've never done this before. I used OBS and it defaulted as an flv file, when it seems I should have used m4v for better quality.